1. Field of the Invention
The invention relates to substrates for mirror supports with reduced weight as well as mirrors with reduced-weight mirror supports.
2. Description of Related Art
Substrates for mirror supports with reduced weight as well as mirrors with reduced-weight mirror supports are frequently utilized in extraterrestrial applications, such as in space travel, for example, in order to be free from atmospheric speckle distortions and deformations from observation points remote from earth as well as also to bypass the continually increasing terrestrial light pollution, which has a contrast-reducing effect on observation results as a background source of light in terrestrial astronomy.
Also in terrestrial astronomy, it is advantageous to make available systems with small mass, since, when the mirror is adjusted or when moving objects are tracked, such as in the observation of stellar bodies on their trajectories, the force required for regulating and resetting decreases with the reduced weight of the moved mass.
In addition to the reduced weight, however, the rigidity of the mirror support or its sagging due to the mirror that is accommodated on it becomes very important.
If at first a pure weight reduction by eliminating mass may appear to be a simple and obvious measure, it becomes immediately clear, however, that very high requirements relative to strength and rigidity are placed on the structure that remains after the elimination of mass.
If one obtains regions of less than half of the original weight, in fact regions of less than two-thirds of the initial weight, then demanding challenges are presented in processing the substrate of the mirror support. This situation becomes particularly more difficult if materials such as glass or glass ceramics are to be finished with high precision.
Various tests have been undertaken to obtain mirror supports with reduced mass and rigidity but which can still be used.
The structure of a mirror support with reduced weight has been produced in which spheres have been assembled with plates in order to obtain in this way a closed rigid structure. The disadvantage of this solution, however, is that such spheres usually have a different thermal expansion behavior than the basic structure of the mirror support, and consequently, with fluctuations in temperature, which are unavoidable in many cases of application, additional deformations may occur. In addition, a high shaping precision cannot be definitively obtained by the hot forming process used in this case.